The Effect of Red Rock Reservoir on the Planktonic Community of the Des Moines River

Abstract

The problem. The objective of this study was to determine the effect of Red Rock Reservoir on the planktonic community of the Des Moines River. Procedure. This was accomplished by (1) measuring primary productivity of the phytoplankton in terms of C14-uptake using standard lake methods in conjunction with a newly designed sample-holding apparatus to overcome most of the problems attributed to water currents, and (2) ascertaining the fate of phytoplankton passing through Red Rock Reservoir. Findings. Primary productivity above Red Rock Reservoir was significantly higher than below Red Rock Reservoir. The values recorded for water temperature, available light, essential nutrients and water velocity showed no correlation to differences in primary production. The greatest correlation was found between primary production and the total number of planktonic organisms per milliliter. Conclusion. Primary production by phytoplankton below Red Rock dam was significantly lower than above Red Rock Reservoir. This difference was apparently due to lower population levels below the dam as a result of cell destruction in passage through Red Rock Reservoir. Recommendations. It is recommended that a similar study be conducted after Saylorville Reservoir has been impounded to assess its impact on primary production.